1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus. More particularly, the present invention relates to a used toner collecting device capable of preventing the used toner from caking, and an image forming apparatus having the same.
2. Description of the Related Art
Generally, an image forming apparatus forms an electrostatic latent image on an image carrying medium by a laser scanning unit (LSU), develops the electrostatic latent image into a toner image by supplying toner particles, transfers the toner image onto a printing paper, and fixes the transferred image onto the printing paper with heat and pressure, thereby producing a desired image. In such an image forming apparatus, a difference in electric potentials between the image carrying medium and a transfer unit, or between the transfer unit and the printing paper, is utilized to produce the desired image. However, the toner image may not be totally transferred to the printing paper while being transferred from the image carrying medium to the transfer unit and from the transfer unit to the printing paper. In other words, toner from the toner image may partially be left on the image carrying medium or the transfer unit. The residual toner (hereinafter, referred to as ‘used toner’) is collected by a used toner collecting device and stored in a used toner receptacle.
FIG. 1 shows an image forming apparatus which is disclosed in Korean Patent Publication No. 2005-040973, which comprises a conventional used toner collecting device 20. Referring to FIG. 1, in such a conventional image forming apparatus 10, when a toner image is transferred sequentially from a photoconductive drum 11, onto a transfer belt 14, and then onto paper P, part of the toner remains on the photoconductive drum 11 or the transfer belt 14. The photoconductive drum 11 and the transfer belt 14 temporarily holds the toner image before the toner image is finally transferred onto the paper P. The image forming apparatus also includes a developing unit 12, a laser scanning unit 15, a transfer roller 16, an electrifying unit 17, and a fixing unit 18.
The used toner collecting device 20 comprises a used toner housing 21 for receiving the used toner T scraped off by a cleaning blade 13 that removes the used toner remaining on the photoconductive drum 11, a conveying auger 23 for moving the used toner T stacked in the used toner housing 21, a conveying duct 22 serving as a connection passage where the used toner T is moved by the conveying auger 23, and a used toner receptacle 24 storing the used toner T moved through the conveying duct 22.
The used toner T removed from the photoconductive drum 11 by the cleaning blade 13 is conveyed to the used toner receptacle 24 by the used toner collecting device 20 so that a difference in height between the cleaning blade 13 and an inlet 24a of the used toner receptacle 24 can be overcome. The used toner receptacle 24 is provided with the inlet 24a for injecting the used toner at an upper part thereof so as to efficiently receive the used toner. The conveying duct 22 includes a conveying coil (not shown) for moving the used toner T. The conveying coil comprises a flight spirally formed on an outer circumference of a rotary shaft. As the conveying coil rotates, the used toner T is conveyed to the used toner receptacle 24.
However, the conventional used toner collecting device 20 occupies a large space in the image forming apparatus 10. As laser printers are becoming smaller and less complicated, the space required by the used toner collecting device should also be reduced. In a compact laser printer, the space for discharging the used toner of the photoconductive drum and the transfer belt is especially limited.
Accordingly, the space for discharging the used toner using a conveying belt is reduced in some compact-sized image forming apparatuses. The used toner does not accumulate in the used toner collecting device comprising the conveying belt when the device normally operates. However, when the used toner collecting device does not fluently discharge the used toner from the photoconductive drum to the used toner receptacle, the used toner gradually accumulates and cakes. Moreover, the used toner may cake at the used toner outlet where the used toner drops into the used toner receptacle.
Accordingly, there is a need for a compact used toner collecting device suitable for use in a compact laser printer, and an image forming apparatus using the same.